As generally indicated above, this invention relates to endless tracks for track-type vehicles, and more particularly to improvements in endless tracks and components therefor which provide for greater life and minimization of repair and maintenance costs.
Conventional endless tracks for use with track-type vehicles, such as crawler tractors, employ a plurality of closely coupled ground engaging track shoes which are carried by an endless track chain. The track chain comprises a plurality of pairs of track links which are articulately interconnected by track pins and track bushings for relative pivotal movement therebetween. The track chain is adapted to be trained over the rollers and sprockets of the vehicle, and the pin and bushing connections provide a drive means for coaction with a chain-driving sprocket whereby the track is forcibly driven by rotational movement of the sprocket.
Although such a track construction has gained wide acceptance, it is subject to several shortcomings. For example, in such prior art track constructions, the track links have along their radially inner edges rail surfaces upon which the rollers and wheels of the track-type vehicle roll. In operation, the rail surfaces are subjected to a high rate of wear, primarily at the longitudinal middle portions thereof, due to rolling contact with the rollers and wheels of the vehicle. It has also been found that wear of the middle portions of the rail surfaces are substantially accelerated due to the longitudinal gaps between adjacent links which in prior endless tracks are relatively large and thereby provide limited support for the rollers of the track-type vehicle. Such wear is further aggravated by the extreme use conditions the endless track is subjected to, either on account of highly corrosive earth conditions or because of abrasive elements such as sand, rocks and the like. When the rail surfaces have worn to such an extent that it affects the overall operation of the endless track, the track links must be repaired or discarded, either of which is relatively costly. Moreover, such maintenance of the endless track normally cannot be done at the work site requiring the return of the endless track to the factory or service garage, thus resulting in lengthy periods when the vehicle cannot be used.
Under the conditions in which the endless tracks operate, small abrasive particles, i.e., sand, mud, rock dust, etc., tend to work their way between the relatively moving parts of the endless track, such as between the counterbores of the track links and track bushings and between the track pins and track bushings. The removal of these foreign particles can normally only be accomplished by disassembling the endless track, which is an extremely expensive and time consuming procedure not adapted to a regular maintenance program. Further, because the track bushings are customarily case hardened and therefore are considerably harder than the track links or pins, the track links and track pins wear more rapidly than the bushings leading to their early replacement. Since track pins and bushings wear unevenly, it has been found that the useful lives of such track pins and bushings can be increased by rotating the same 180.degree., but such rotation requires disassembly and reassembly of the endless track, which is costly and time consuming and normally cannot be done at the work site.
Of course, many of the aforesaid problems can be minimized by providing dust seals to prevent abrasive elements from entering between the bearing surfaces of the relatively moving parts. The use of seals in endless tracks is well known, however, many of these dust seals are expensive to manufacture and others fail to provide adequate seals allowing entry of the abrasive elements.